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Revenue - Summary of Revenue From Contracts with Customers (Detail) - TWD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Receivables from contracts with customers [abstract]      
Revenue from contracts with customers $ 23,011,381 $ 20,337,881 $ 18,480,027